Motor drive control device

ABSTRACT

A motor drive control device driving a motor having a first system coil and a second system coil, the motor drive control device comprising: a first drive circuit controlling energization of the first system coil; a second drive circuit controlling energization of the second system coil; and a signal output circuit detecting a first voltage that is a voltage at a middle point of the first system coil and a second voltage that is a voltage at a middle point of the second system coil, and outputting an output signal concerning whether or not any one of the first system coil and the second system coil is in an open state, based on a detection result of the first voltage and a detection result of the second voltage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2019-37863, filed Mar. 1, 2019, which is hereby incorporated byreference in its entirety.

BACKGROUND Technical Field

The present disclosure relates to a motor drive control device, andparticularly relates to a motor drive control device having two systemsof drive circuits.

Background Art

In the past, a motor drive device driving a single-phase motor has beendisclosed (for example, Japanese Patent Application Laid-Open No.2009-77543).

SUMMARY

Here, failures may occur in a drive circuit of the motor drive controldevice so that it becomes impossible to drive the motor. When it becomesimpossible to drive the motor as mentioned above in use of driving themotor in a prescribed rotational direction (forward direction), forexample, and an external force works to forcibly rotate the motor in adirection opposite to the prescribed rotational direction (rotateinversely), troubles may occur.

For example, in a case of driving a fan motor by the motor drive controldevice, if a drive coil of the motor disconnects to cause a drivecircuit of the motor drive control device to not normally function, thedriving of the fan motor stops. In such case, when air flows into thestopped fan motor due to an operation of another fan motor used alongwith the stopped fan motor, for example, the stopped fan motor may berotated inversely. For example, in a case where a plurality of fanmotors are used for cooling a device surrounded by a housing and one ofthe fan motors is rotated inversely in a manner described above,decrease in an internal pressure of the device may be caused todeteriorate a cooling function, possibly affecting functions of thedevice. Therefore, it is necessary to continue a forward rotation of thefan motor as much as possible.

As a solution to solve the above problem, by including two systems ofdrive circuits as the motor drive control device, even in a case whereone of the drive circuits is failed, the other drive circuit can be usedto allow to the driving of the fan motor to continue.

Here, in a case where such a motor drive control circuit is providedwith two systems of drive circuits, it may be convenient if the motordrive control circuit and devices using it and the like can becontrolled depending on how drive state each drive circuit is in (forexample, whether each drive circuit is in a normally driving state) andif a user can be notified of the drive state of the motor (whethernormal or abnormal).

The present disclosure is related to providing a motor drive controldevice capable of continuing a forward rotation of a motor as much aspossible and capable of externally notifying a drive state.

In accordance with one aspect of the present disclosure, a motor drivecontrol device driving a motor having a first system coil and a secondsystem coil, the motor drive control device including a first drivecircuit controlling energization of the first system coil, a seconddrive circuit controlling energization of the second system coil, and asignal output circuit detecting a first voltage that is a voltage at amiddle point of the first system coil and a second voltage that is avoltage at a middle point of the second system coil, and outputting anoutput signal concerning whether or not any one of the first system coiland the second system coil is in an open state, based on a detectionresult of the first voltage and a detection result of the secondvoltage.

Preferably, the motor drive control device further includes an externaloutput terminal from which the output signal is output, wherein thesignal output circuit outputs, when the motor is normally driven, afirst output signal as the output signal from the external outputterminal, and outputs, when any one of the first system coil and thesecond system coil is in the open state, a second output signalindicating that the relevant one coil is in the open state, as theoutput signal, from the external output terminal.

Preferably, the first output signal is a signal of which a voltageperiodically varies with a rotation of the motor, and the second outputsignal is a signal of which a voltage is fixed.

Preferably, the external output terminal is connected to an outputterminal of the first drive circuit, and the first output signal is asignal output from the output terminal of the first drive circuit.

Preferably, the signal output circuit includes a comparison unitcomparing the first voltage with a reference voltage and comparing thesecond voltage with the reference voltage, and a switching circuitoutputting a switching signal, based on a comparison result of thecomparison unit, and outputs the output signal in accordance with theswitching signal.

Preferably, the signal output circuit further includes an output signalholding circuit holding the comparison result of the comparison unit fora predetermined time period.

Preferably, the signal output circuit outputs an output signalindicating that any one of the first system coil and the second systemcoil is in the open state, when any of the first voltage and the secondvoltage is equal to or more than a predetermined value.

According to these disclosures, a motor drive control device capable ofcontinuing a forward rotation of a motor as much as possible and capableof externally notifying a drive state can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a configuration of a motor drivecontrol device according to one of embodiments of the presentdisclosure.

FIG. 2 is a diagram illustrating a configuration of an open decisioncircuit.

FIG. 3 is a table illustrating operations of the motor drive controldevice.

FIG. 4 is a first flowchart illustrating an operation performed by themotor drive control device.

FIG. 5 is a second flowchart illustrating an operation performed by themotor drive control device.

FIG. 6 is a diagram illustrating a waveform example of an absolutevoltage of a first midpoint voltage.

FIG. 7 is a third flowchart illustrating an operation performed by themotor drive control device.

FIG. 8 a diagram illustrating a configuration of an open decisioncircuit according to a first variant of the present embodiment.

FIG. 9 a diagram illustrating a configuration of an open decisioncircuit according to a second variant of the present embodiment.

DETAILED DESCRIPTION

Hereinafter, a motor drive control device according to embodiments ofthe present disclosure will be described.

Embodiments

FIG. 1 is a diagram illustrating a configuration of a motor drivecontrol device 1 according to one of embodiments of the presentdisclosure.

As illustrate in FIG. 1, a motor drive control device 1 is used for amotor device having a motor 50. The motor device includes two positiondetectors 41 and 42 outputting position signals in accordance with arotational position of the motor 50. The motor drive control device 1 isexternally supplied with a direct-current power source voltage Vdc.

The motor drive control device 1 has an external input terminal to whicha signal is input from an outside device and an external output terminal29 for outputting a signal to an outside device. The motor drive controldevice 1 is connected to a host device 600.

A speed command signal Sc output from the host device 600 is input tothe external input terminal of the motor drive control device 1. Themotor drive control device 1 drives the motor 50 in accordance with theinput speed command signal Sc.

An output signal So is output from the external output terminal 29 ofthe motor drive control device 1 to the host device 600. The outputsignal So is a signal concerning a state of the motor 50. For example,an FG signal having a frequency corresponding to an actual rotationalfrequency of the motor 50 is output as the output signal So. The hostdevice 600 can know the state of motor 50, based on the output signal Sooutput from the motor drive control device 1. Then, the host device 600can control an operation of the motor device depending on the state ofthe motor 50, such as by outputting the speed command signal Sc to themotor drive control device 1.

The motor 50 includes a first system coil 80 and a second system coil 80b wound around teeth (not illustrated). Note that each of the firstsystem coil 80 and the second system coil 80 b may be constituted by onecoil.

In the present embodiment, the motor drive control device 1 includes afirst drive circuit 10 controlling energization of the first system coil80, a second drive circuit 10 b controlling energization of the secondsystem coil 80 b, and a signal output circuit 20.

The first drive circuit 10 includes a first control circuit unit 12including an inverter circuit (not illustrated) energizing the firstsystem coil 80 and a drive control circuit controlling the invertercircuit, and a fuse 19 provided on a power source supply path from thepower source voltage Vdc to the first control circuit unit 12, that is,a power source supply path of the first drive circuit 10. The seconddrive circuit 10 b includes a second control circuit unit 12 b includingan inverter circuit (not illustrated) energizing the second system coil80 b and a drive control circuit controlling the inverter circuit, and afuse 19 b provided on a power source supply path from the power sourcevoltage Vdc to the second control circuit unit 12 b, that is, a powersource supply path of the second drive circuit 10 b.

Each of the first control circuit unit 12 and the second control circuitunit 12 b is one integrated circuit (IC) including the inverter circuitand the drive control circuit. Note that the configuration of the firstcontrol circuit unit 12 or the second control circuit unit 12 b is notlimited to that described above, but may not be the integrated circuit,or only a part of the first control circuit unit 12 or the secondcontrol circuit unit 12 b may be an integrated circuit.

In the present embodiment, both the first control circuit unit 12 andthe second control circuit unit 12 b are configured, as hardware, usinga general IC having the same configuration. Each of the first controlcircuit unit 12 and the second control circuit unit 12 b has a Vccterminal (a Vcc terminal 121, a Vcc terminal 121 b), a PWM terminal (aPWM terminal 125, a PWM terminal 125 b), an Out1 terminal, an Out2terminal, and the like. The Vcc terminals 121 and 121 b are connected tothe power source voltage Vdc via the fuses 19 and 19 b, respectively.The PWM terminals 125 and 125 b are connected to the external inputterminal, and are terminals to which the speed command signals Sc areinput. The Out1 terminals and the Out2 terminals are terminals forenergizing the coils 80 and 80 b, and connected to the coils 80 and 80b. The first control circuit unit 12 has an output terminal (FGterminal) 123. The second control circuit unit 12 b is also providedwith an output terminal, though illustration thereof is omitted. Notethat the first control circuit unit 12 and the second control circuitunit 12 b may have the configurations as hardware different from eachother.

The first position detector 41 is connected to the first drive circuit10. The second position detector 42 is connected to the second drivecircuit 10 b. The first position detector 41 is arranged at a positioncorresponding to the first system coil 80. The second position detector42 is arranged at a position corresponding to the second system coil 80b.

Two position detectors 41 and 42 output position detection signals inaccordance with a position of a rotor of the motor 50. The firstposition detector 41 outputs the position detection signal to the firstcontrol circuit unit 12. The second position detector 42 outputs theposition detection signal to the second control circuit unit 12 b. Notethat in the present embodiment, the first and second position detectors41 and 42 are Hall elements. Each Hall element outputs, as the positiondetection signal, a Hall signal having a positive or negative polarity.Note that the first and second position detectors 41 and 42 are notlimited to the elements the same as each other, and are not limited tothe Hall elements.

The output terminal 123 is an FG terminal for outputting the FG signal.Note that the output terminal 123 may be a terminal provided so as to beable to be configured in advance to function as the FG terminal, or asan RD terminal for outputting a lock signal indicating whether or notthe motor 50 is in a locked state. A signal line 31 connected to theoutput terminal 123 is connected to the signal output circuit 20.

The speed command signal Sc and the position detection signal outputfrom the first position detector 41 are input to the first controlcircuit unit 12. The speed command signal Sc and the position detectionsignal output from the second position detector 42 are input to thesecond control circuit unit 12 b. The speed command signal Sc is asignal concerning the driving of the motor 50, and, to be more specific,is a signal of a voltage corresponding to a rotational frequency (targetrotational frequency) at which the motor 50 is rotated. For example, thespeed command signal Sc is a PWM (pulse width modulation) signal of dutydepending on the target rotational frequency with a high level of 5volts. Note that the speed command signal Sc may be another kind ofsignal such as a clock signal having a frequency depending on the targetrotational frequency.

The drive control circuit of each of the first control circuit unit 12and the second control circuit unit 12 b outputs a signal for operatingthe inverter circuit, based on the position detection signal to controlthe operation of the inverter circuit. Each of the first control circuitunit 12 and the second control circuit unit 12 b detects the actualrotational frequency (the frequency of actual rotations) of the motor50, based on the position detection signal to control an ON/OFFoperation of a switching element included in the inverter circuit sothat the actual rotational frequency of the motor 50 becomes arotational frequency corresponding to the input speed command.

Specifically, the first drive circuit 10 is configured to controlenergization of the first system coil 80 based on the target rotationalfrequency externally specified. The second drive circuit 10 b isconfigured to control energization of the second system coil 80 b basedon the target rotational frequency externally specified.

The inverter circuit of each of the first control circuit unit 12 andthe second control circuit unit 12 b energizes the coils 80 and 80 b sothat directions of currents flowing in the coils 80 and 80 b included inthe motor 50 are switched at a timing in accordance with the positiondetection signal based on the signal output from the drive controlcircuit.

As described above, the first control circuit unit 12 outputs from theoutput terminal 123 the FG signal of which a voltage repeats a highlevel and a low level at a frequency corresponding to the actualrotational frequency of the motor 50. The FG signal is a signal of whicha voltage periodically varies with a rotation of the motor 50.Specifically, the first drive circuit 10 outputs the signal concerningthe drive state of the motor 50. The FG signal is input via the signalline 31 to the signal output circuit 20. Note that, instead of the FGsignal, the Hall signal or the like of which a voltage periodicallyvaries with the rotation of the motor 50 may be output.

In the present embodiment, the output terminal 123 is configured tooutput the signal in a so-called open drain manner. Specifically, theoutput terminal 123 is pulled up to a predetermined voltage to be usedso that the voltage becomes a high level at a high impedance (openstate). This allows the FG signal having a high level or low levelvoltage to be output.

The signal output circuit 20 is connected to a middle point 81 of thefirst system coil 80 and a middle point 81 b of the second system coil80 b. Note that, here, the middle points 81 and 81 b do not strictlyrefer to points bisecting the coils 80 and 80 b, but refer to pointssubstantially bisecting the coils 80 and 80 b. The middle points 81 and81 b may be also referred to as midpoints 81 and 81 b.

The signal output circuit 20 detects a first midpoint voltage VA (anexample of a first voltage) that is a voltage at the middle point 81 ofthe first system coil 80 and a second midpoint voltage VB (an example ofa second voltage) that is a voltage at the middle point 81 b of thesecond system coil 80 b. The signal output circuit 20 outputs the outputsignal So concerning the state of the motor 50, based on a detectionresult of the first midpoint voltage VA and a detection result of thesecond midpoint voltage VB. To be more specific, the signal outputcircuit 20 outputs the output signal So concerning whether or not anyone of the first system coil 80 and the second system coil 80 b is inthe open state, based on the detection result of the first midpointvoltage VA and the detection result of the second midpoint voltage VB.The signal output circuit 20 outputs the first output signal as theoutput signal So from the external output terminal 29 when the motor 50is normally driven, and outputs the second output signal as the outputsignal So from the external output terminal 29 when any one of the firstsystem coil 80 and the second system coil 80 b is in the open state, thesecond output signal indicating that the relevant one coil is in theopen state.

In the present embodiment, the signal line 31 is connected to theexternal output terminal 29 in the signal output circuit 20.Specifically, the external output terminal 29 is connected via thesignal line 31 to the output terminal 123 of the first drive circuit 10,and the first output signal is the FG signal output from the outputterminal 123 of the first drive circuit 10. In other words, when themotor 50 is normally driven, the signal output circuit 20 outputs, asthe first output signal, the FG signal that is output from the outputterminal 123, from the external output terminal 29.

On the other hands, when any one of the first system coil 80 and thesecond system coil 80 b is in the open state, the signal output circuit20 outputs the second output signal indicating that the relevant onecoil is in the open state and does not output the FG signal. The secondoutput signal is, for example, a signal (Low signal) of which a voltageis fixed to a ground potential. Note that the second output signal isnot limited to the Low signal, but, for example, may be a signal ofwhich a voltage is fixed, such as the High signal of which a voltage isfixed to a high level. That is, the second output signal may be a signaldifferent from the first output signal.

The signal output circuit 20 includes the open decision circuit 21. Theopen decision circuit 21 is connected to the power source voltage Vdc.

The open decision circuit 21 is connected to the midpoint 81 of thefirst system coil 80 and the midpoint 81 b of the second system coil 80b. The open decision circuit 21 detects the first midpoint voltage VAthat is the voltage at the middle point 81 of the first system coil 80and the second midpoint voltage VB that is the voltage at the middlepoint 81 b of the second system coil 80 b. The open decision circuit 21outputs a switching signal. The switching signal is output to aconnection point P1 on the signal line 31 connecting the output terminal123 to the external output terminal 29.

FIG. 2 is a diagram illustrating a configuration of the open decisioncircuit 21.

As illustrated in FIG. 2, the open decision circuit 21 of the signaloutput circuit 20 includes a voltage comparison circuit 23 (an exampleof a comparison unit) that is connected to the midpoint 81 of the firstsystem coil 80 and the midpoint 81 b of the second system coil 80 b andhas two comparators CMP1 and CMP2, an output signal holding circuit 24,and a decision signal output circuit 25 (an example of a switchingcircuit) that outputs a switching signal based on a comparison result ofthe voltage comparison circuit 23. The open decision circuit 21 outputsthe switching signal from the decision signal output circuit 25 to theconnection point P1. The signal output circuit 20 outputs the outputsignal So in accordance with the switching signal.

Each of the midpoint 81 of the first system coil 80 and the midpoint 81b of the second system coil 80 b is connected to the voltage comparisoncircuit 23. The first midpoint voltage VA at the midpoint 81 and thesecond midpoint voltage VB at the midpoint 81 b are input to the voltagecomparison circuit 23. A reference voltage obtained by dividing thepower source voltage Vdc by a resistance R71 and a resistance R72 isinput to the voltage comparison circuit 23.

The voltage comparison circuit 23 includes resistances R29 and R49, anda capacitor C71, besides an IC 71 having two comparators CMP1 and CMP2.Note that the resistances R29 and R49 may not be provided. The powersource voltage Vdc is applied via the resistances R29 and R49 to theoutput terminals P7 and P2 of the comparators CMP1 and CMP2,respectively, and the capacitor C71 for smoothing is provided on theirlines.

The voltage comparison circuit 23 compares the first midpoint voltage VAwith the reference voltage and compares the second midpoint voltage VBwith the reference voltage to output the respective comparison results.Specifically, the reference voltage is input to an inverting inputterminal of the comparator CMP1. The first midpoint voltage VA is inputto a non-inverting input terminal of the comparator CMP1. The referencevoltage is input to an inverting input terminal of the comparator CMP2.The second midpoint voltage VB is input to a non-inverting inputterminal of the comparator CMP2.

An output from the output terminal P7 of the comparator CMP1 and anoutput from the output terminal P2 of the comparator CMP2 are input tothe output signal holding circuit 24. Specifically, the comparisonresult of the voltage comparison circuit 23 is input to the outputsignal holding circuit 24. The output signal holding circuit 24 includestwo diodes D22 and D42, and one capacitor C72. An anode of each of twodiodes D22 and D42 are respectively connected to the output terminal P7and the resistance R29 and to the output terminal P2 and the resistanceR49, cathodes of two diodes D22 and D42 are connected to each other, andthe capacitor C72 is provided between a connection point of the diodesand the ground potential. The connection point of two diodes D22 and D42is connected to the decision signal output circuit 25.

The output signal holding circuit 24 can hold the comparison result ofthe voltage comparison circuit 23 for a predetermined time period andoutput to the decision signal output circuit 25. Specifically, when thecomparison result of the voltage comparison circuit 23 varies, charge ordischarge of the capacitor C72 is performed in the output signal holdingcircuit 24 such that an output of the output signal holding circuit 24follows the comparison result of the voltage comparison circuit 23 aftera little time elapses. Note that the predetermined time period for whichthe comparison result of the voltage comparison circuit 23 is held maybe adequately set depending on a capacitance of the capacitor C72 or thelike.

The decision signal output circuit 25 is connected to the groundpotential and the connection point P1 that is on the signal line 31coupling the output terminal 123 with the external output terminal 29.The comparison result of the voltage comparison circuit 23 is input viathe output signal holding circuit 24 to the decision signal outputcircuit 25. The decision signal output circuit 25 switches depending onthe voltage output from the output signal holding circuit 24 whether toconnect the external output terminal 29 with the ground potential.

Specifically, the decision signal output circuit 25 provides with afield-effect transistor Q72 (hereinafter, also simply referred to as atransistor Q72) a gate of which is connected via a resistance to theoutput of the output signal holding circuit 24. A source of thetransistor Q72 is connected to the ground potential, and a drain of thetransistor Q72 is connected to the connection point P1. A switchingoperation of the transistor Q72 is performed, and thereby, whether toconnect the external output terminal 29 and the ground potential isswitched.

Such a switching signal switches whether the external output terminal 29is the ground potential or the high impedance. When the external outputterminal 29 is connected to the ground potential, the second outputsignal, that is the Low signal, output from the signal output circuit20, and when the external output terminal 29 has the high impedance, thefirst output signal, that is, the FG signal, is output from the signaloutput circuit 20. The signal output circuit 20 outputs, as the outputsignal So, the first output signal to the external output terminal 29,when the motor 50 is normally driven. When any one of the first systemcoil 80 and the second system coil 80 b is in the open state, the signaloutput circuit 20 outputs, as the output signal So, the second outputsignal indicating that the relevant one coil is in the open state fromthe external output terminal 29, as described later. In other words,when any one of the first system coil 80 and the second system coil 80 bis in the open state, the open decision circuit 21 operates such thatthe second output signal is output from the signal output circuit 20, asdescribed later. By doing so, the host device 600 is notified, based onthe output signal So, of whether the motor 50 is in a rotating state, orotherwise, whether any one of the first system coil 80 and the secondsystem coil 80 b is in the open state.

Here, in the present embodiment, when any of the first midpoint voltageVA and the second midpoint voltage VB has a predetermined value or more,the signal output circuit 20 outputs the output signal So indicatingthat any one of the first system coil 80 and the second system coil 80 bis in the open state. Specifically, when any one of the first systemcoil 80 and the second system coil 80 b is in the open state, any of thefirst midpoint voltage VA and the second midpoint voltage VB is equal toor more than a predetermined reference voltage, and the second outputsignal is output as the output signal So. In a case where both the firstmidpoint voltage VA and the second midpoint voltage VB are not equal toor more than the reference voltage, the first output signal is output asthe output signal So.

Note that the reference voltage may be adequately set, for example, maybe set to three-fourths of a magnitude of the power source voltage Vdc.The magnitude of the reference voltage can be adjusted depending onresistance values of the resistances R71 and R72. The magnitude of thereference voltage is not limited to those described above. The magnitudeof the reference voltage may be larger than magnitudes of the midpointvoltages VA and VB when the first system coil 80 and the second systemcoil 80 b are not disconnected, and smaller than the magnitude of thepower source voltage Vdc. The reference voltage is not limited to thosegenerated by dividing the power source voltage Vdc.

The operations of the respective components of the signal output circuit20 and the output signal So output from the signal output circuit 20 maybe summarized for each state of the motor 50 as below.

FIG. 3 is a table illustrating the operations of the motor drive controldevice 1.

In the table illustrated in FIG. 3, states of “normal”, “first systemcoil disconnection”, and “second system coil disconnection” are in rows,and the operations or magnitudes of the voltages of the respectivecomponents in the motor drive control device 1 are in columns. The“normal” is a state where the motor 50 is normally driven. The “firstsystem coil disconnection” is a state where the first system coil 80disconnects. The “second system coil disconnection” is a state where thesecond system coil 80 b disconnects.

In the columns, shown are magnitudes of the power source voltage Vdc,the first midpoint voltage VA, the second midpoint voltage VB, and thereference voltage, and states of the output terminal P7 of thecomparator CMP1, states of the output terminal P2 of the comparatorCMP2, states of the transistor Q72, and the output signal So.

In FIG. 3, notations of the like for the signal and states are as below.“Vin” represents a magnitude of the power source voltage Vdc. “FGsignal” represents that an FG signal is output. “Low” represents that asignal of which a voltage is fixed to the ground potential is output. Asfor the output terminals P7 and P2, “OFF” represents that theseterminals are connected to the ground potential, and “ON” representsthat these terminals are at voltages on the basis of the power sourcevoltage Vdc. As for the transistor Q72, “OFF” represents that thetransistor Q72 is in an off-state, that is, a state where the decisionsignal output circuit 25 does not connect the external output terminal29 with the ground potential, “ON” represents that the transistor Q72 isin an on-state, that is, a state where the decision signal outputcircuit 25 connects the external output terminal 29 with the groundpotential. Note that the magnitude of the reference voltage is set to“¾Vin” as a specific example.

FIG. 4 is a first flowchart illustrating the operation performed by themotor drive control device 1.

The motor drive control device 1 operates as below, caused by the signaloutput circuit 20 has a as described above circuit configuration.

At step S11, the motor drive control device 1 operates so that the motor50 performs a steady rotation. This state corresponds to a state of“normal” in the table shown in FIG. 3. Specifically, the FG signal isoutput from the output terminal 123. When both the first system coil 80and the second system coil 80 b do not disconnect, each of maximumvalues of the first midpoint voltage VA and the second midpoint voltageVB is a voltage (“Vin/2”) that is one-half of the magnitude of the powersource voltage Vdc. Since the reference voltage is “¾Vin”, the outputterminals P7 and P2 are “OFF”, and the transistor Q72 is in theoff-state. Therefore, the first output signal (FG signal) is output, asthe output signal So, from the external output terminal 29. The hostdevice 600 can detect the rotational frequency of the motor 50, based onthe output signal So.

At step S12, when the first system coil 80 of the motor 50 disconnects(YES), the process goes to step S31 (illustrated in FIG. 5). In theother case (NO), the process goes to step S13.

At step S13, when the second system coil 80 b of the motor 50disconnects (YES), the process goes to step S41 (illustrated in FIG. 6).In the other case (NO), the process goes to step S11. Specifically, ifthe state where the motor 50 is normal continues (NO at both step S12and step S13), the operation of step S11 continues.

FIG. 5 is a second flowchart illustrating the operation performed by themotor drive control device 1.

When the first system coil 80 of the motor 50 disconnects, the motordrive control device 1 operates as illustrated in FIG. 5. This statecorresponds to a state of “first system coil disconnection” in the tableshown in FIG. 3.

Specifically, if the first system coil 80 disconnects while the motor 50is driven, the maximum value of the first midpoint voltage VA rises(step S31). The maximum value of the first midpoint voltage VA becomes“Vin”, and the maximum value the second midpoint voltage VB remains“Vin/2”.

FIG. 6 is a diagram illustrating a waveform example of the firstmidpoint voltage VA.

As illustrated in a lower tier in FIG. 6, at a normal time, an absolutevalue of the first midpoint voltage VA is “Vin/2”. However, if the firstsystem coil 80 disconnects, the current does not flow in the firstsystem coil 80. For this reason, as illustrated in an upper tier in FIG.6, only when a voltage is applied in a predetermined direction, theabsolute value of the first midpoint voltage VA becomes “Vin”. Note thatthe second midpoint voltage VB has an aspect similar to that illustratedin FIG. 6 at the normal time and when the second system coil 80 bdisconnects.

Returning to FIG. 5, if the maximum value of the first midpoint voltageVA rises as described above, the voltage of the output terminal P7 ofthe comparator CMP1 in the voltage comparison circuit 23 turns to ON(high level) (step S32). At this time, the voltage of the outputterminal P2 of the comparator CMP2 is OFF (low level).

When the voltage of the output terminal P7 of the comparator CMP1 turnsto ON, the transistor Q72 turns to the on-state in the decision signaloutput circuit 25 (step S33).

Then, the signal line 31 is connected to the ground potential, and theexternal output terminal 29 becomes the ground potential. Specifically,the second output signal (the signal of which the voltage is fixed tothe ground potential) is output as the output signal So (step S34). Thehigher device 600 detects a state where at least one of the first systemcoil 80 and the second system coil 80 b of the motor 50 disconnects,based on the output signal So.

Note that in this case, the second drive circuit 10 b continues to drivethe motor 50. This allows the rotation of the motor 50 to be maintained,preventing the motor 50 from inversely rotating owing to an externalforce or the like.

FIG. 7 is a third flowchart illustrating the operation performed by themotor drive control device 1.

When the second system coil 80 b of the motor 50 disconnects, the motordrive control device 1 operates as illustrated in FIG. 7. This statecorresponds to a state of “second system coil disconnection” in thetable shown in FIG. 3.

Specifically, if the second system coil 80 b disconnects while the motor50 is driven, the maximum value of the second midpoint voltage VB rises(step S41). The maximum value of the second midpoint voltage VB becomes“Vin”, and the maximum value the first midpoint voltage VA remains“Vin/2”.

Accordingly, the voltage of the output terminal P2 of the comparatorCMP2 in the voltage comparison circuit 23 turns to ON (high level) (stepS42). At this time, the voltage of the output terminal P7 of thecomparator CMP1 is OFF (low level).

When the voltage of the output terminal P2 of the comparator CMP2 turnsto ON, the transistor Q72 turns to the on-state in the decision signaloutput circuit 25 (step S43).

Then, the signal line 31 is connected to the ground potential, and theexternal output terminal 29 becomes the ground potential. Specifically,the second output signal (the signal of which the voltage is fixed tothe ground potential) is output as the output signal So (step S44). Thehost device 600 detects a state where at least one of the first systemcoil 80 and the second system coil 80 b of the motor 50 disconnects,based on the output signal So.

Note that in this case, the first drive circuit 10 continues to drivethe motor 50. This allows the rotation of the motor 50 to be maintained,preventing the motor 50 from inversely rotating owing to an externalforce or the like.

As described above, in the present embodiment, the output signal So isoutput which concerns whether or not any one of the first system coil 80and the second system coil 80 b is in the open state, based on thedetection result of the first midpoint voltage VA and the detectionresult of the second midpoint voltage VB. Therefore, notification thatany one of the first system coil 80 and the second system coil 80 bbecomes the open state in the motor 50 can be made to the outside.

The output signal So concerning whether or not any one of the firstsystem coil 80 and the second system coil 80 b is in the open state isoutput from one external output terminal 29 from which the first outputsignal concerning the state of the motor 50 is output when the motor 50is normally driven. Therefore, the number of signal lines connectingbetween the motor drive control device 1 and the host device 600 can bereduced, and the configuration of the motor drive control device 1 canbe simplified. In the present embodiment, by use of the external outputterminal 29 from which the FG signal is output as the output signal Soat the normal time, notification that any one of the first system coil80 and the second system coil 80 b becomes the open state can be made tothe outside by outputting the second output signal as the output signalSo. Therefore, the configuration of the motor drive control device 1 canbe simplified.

In the present embodiment, a circuit configuration inside the motordrive control device 1 is simple. A large scale integrated circuit orthe like does not be used in order to output the output signal So (thesecond output signal) concerning whether or not any one of the firstsystem coil 80 and the second system coil 80 b is in the open state,allowing a manufacturing cost of the motor drive control device 1 to bereduced. Since a simple small integrated circuit can be used toconfigure the motor drive control device 1, the motor drive controldevice 1 can be downsized.

In the present embodiment, the comparison result of the voltagecomparison circuit 23 is held by the output signal holding circuit 24for a predetermined time period. This allows a charge corresponding tocomparison result to be held by the diodes D22 and D42 and the capacitorC72 even while the motor 50 is rotating where the first midpoint voltageVA and the second midpoint voltage VB change every moment. Therefore,even while the motor 50 is rotating, the output signal So can beappropriately output depending on whether or not any one of the firstsystem coil 80 and the second system coil 80 b is in the open state.

For example, in a case where the motor 50 is a fan motor, even if afailure occurs in the motor 50, rotation of the fan may be expected tocontinue. In a case where the motor 50 is used for such an application,since two systems of winding structures and circuit configurations ofthe motor 50 are provided in the motor drive control device 1, even if afailure occurs in one system, the remaining one system can continue torotate motor 50. However, in the case where the remaining one systemcontinues to rotate the motor 50 like this, if the remaining one systemis failed, the rotation of the motor 50 stops, and therefore, it ispreferable to rapidly notify the outside of the system failure even whenonly one system is failed, and take countermeasures. In the presentembodiment, in a case where one of the coils 80 and 80 b of the motor 50disconnects, the disconnection is detected by detecting the midpointvoltages VA and VB, and the second output signal indicating thedisconnection is output as the output signal So. Therefore, while theremaining one system continues to rotate the motor 50, such a failurecan be notified to the user. Since a circuit having an inexpensiveconfiguration is used, without using a large scale and expensivemicrocomputer, the manufacturing cost of the motor drive control device1 can be kept low.

Others

The circuit configuration of the motor drive control device is notlimited to the specific example illustrated in the embodiment describedabove. The individual configuration in the embodiment described abovemay be adequately combined with the configuration a part of which ismodified, or may be partially substituted to be adapted to an object ofthe present disclosure. In the embodiment described above, a part of thecomponents or functions may be omitted. In addition to the above,various circuit configurations configured to be adapted to the object ofthe present disclosure can be applied.

For example, the decision signal output circuit may be constituted usinga general transistor or comparator.

The voltage comparison circuit may be constituted using a microcomputeror the like.

Additionally, the circuit configuration of the open decision circuit maybe as below, for example. In the following description, componentssimilar to the embodiment described above is designated by the samereference signs.

FIG. 8 a diagram illustrating a configuration of an open decisioncircuit 421 according to a first variant of the present embodiment.

As illustrated in FIG. 8, in the open decision circuit 421, a voltagecomparison circuit 423 includes only one comparator CMP1, and an outputsignal holding circuit 424 includes three diodes D22, D42, and D72.

An anode of the diode D22 is connected to the midpoint 81 of the firstsystem coil 80, and an anode of the diode D42 is connected to themidpoint 81 b of the second system coil 80 b. Cathodes of the diode D22and the diode D42 are coupled to each other, and a coupling point of thediodes is connected to a non-inverting input terminal of the comparatorCMP1. The reference voltage is input to the inverting input terminal ofthe comparator CMP1, and the first midpoint voltage VA and the secondmidpoint voltage VB are input to the non-inverting input terminal. Theoutput terminal of the comparator CMP1 is input via the diode D72 to thedecision signal output circuit 25.

Even such a circuit configuration is used, the output signal So isoutput similarly to the embodiment described above. Specifically, whenany one of the first system coil 80 and the second system coil 80 b isin the open state, since an absolute value of any of the first midpointvoltage VA and the second midpoint voltage VB rises, the transistor Q72turns to “ON”. Therefore, the same effect as the above is obtained. Insuch a circuit configuration, since the number of elements is smallerthan the circuit configuration in the embodiment described above, andthe cost reduction can be achieved.

FIG. 9 a diagram illustrating a configuration of an open decisioncircuit 521 according to a second variant of the present embodiment.

As illustrated in FIG. 9, in the open decision circuit 521, the voltagecomparison circuit 423 similar to the first variant is provided, and anoutput signal holding circuit 524 is provided to a stage prior to thevoltage comparison circuit 423. The output signal holding circuit 524includes two diodes D22 and D42 and one capacitor C72 similarly to theembodiment described above.

An anode of the diode D22 is connected to the midpoint 81 of the firstsystem coil 80, and an anode of the diode D42 is connected to themidpoint 81 b of the second system coil 80 b. A coupling point ofcathodes of the diode D22 and the diode D42 is connected to anon-inverting input terminal of the comparator CMP1. Specifically, thereference voltage is input to the inverting input terminal of thecomparator CMP1, and the first midpoint voltage VA and the secondmidpoint voltage VB are input to the non-inverting input terminal. Theoutput terminal of the comparator CMP1 is input to the decision signaloutput circuit 25.

Even such a circuit configuration is used, the output signal So isoutput similarly to the embodiment described above. Specifically, whenany one of the first system coil 80 and the second system coil 80 b isin the open state, since an absolute value of any of the first midpointvoltage VA and the second midpoint voltage VB rises, the transistor Q72turns to “ON”. Therefore, the same effect as the above is obtained. Insuch a circuit configuration, since the number of elements is smallerthan the circuit configuration in the embodiment described above, andthe cost reduction can be achieved.

In the second variant, the capacitor C72 is provided between theconnection point of the diodes D22 and D42 and the ground potential,which allows even when one of the first midpoint voltage VA and thesecond midpoint voltage VB varies, a voltage of the non-inverting inputterminal of the comparator CMP1 is maintained for a predetermined timeperiod. In other words, the output signal holding circuit 24 functionssuch that the comparison result of the voltage comparison circuit 423 ismaintained for a predetermined time period, even when one of the firstmidpoint voltage VA and the second midpoint voltage VB varies.Therefore, even while the motor 50 is rotating, the output signal So canbe appropriately output depending on whether or not any one of the firstsystem coil 80 and the second system coil 80 b is in the open state.

Each of the first control circuit unit and the second control circuitunit may not have the inverter circuit built-in. Each of the first drivecircuit and the second drive circuit may include an inverter circuitconstituted by a switching element such as an FET, and a control circuitunit controlling operations of the inverter circuit.

The motor driven by the motor drive control device according to thepresent embodiment may not be limited the type described in the aboveembodiment. The motor driven by the motor drive control device may notbe a single-phase motor, and the number of phases is not limited.

The control circuit unit of each drive circuit is not limited to ageneral IC.

The number of position detectors is not limited to two. More positiondetectors may be used. The detection of the rotational position of themotor is not limited to a method using a Hall sensor.

The above embodiment is to be construed as exemplification in allmatters and not limiting. The scope of the present disclosure is shownnot in the above description but in the Claims, and is intended toinclude all modifications in the meaning and scope equivalent to theClaims.

What is claimed is:
 1. A motor drive control device driving a motorhaving a first system coil and a second system coil, the motor drivecontrol device comprising: a first drive circuit controllingenergization of the first system coil; a second drive circuitcontrolling energization of the second system coil; a signal outputcircuit detecting a first voltage that is a voltage at a middle point ofthe first system coil and a second voltage that is a voltage at a middlepoint of the second system coil, and outputting an output signalconcerning whether or not any one of the first system coil and thesecond system coil is in an open state, based on a detection result ofthe first voltage and a detection result of the second voltage; and anexternal output terminal from which the output signal is output, whereinthe signal output circuit outputs, when the motor is normally driven, afirst output signal as the output signal from the external outputterminal, and outputs, when any one of the first system coil and thesecond system coil is in the open state, a second output signalindicating that the relevant one coil is in the open state, as theoutput signal, from the external output terminal.
 2. The motor drivecontrol device according to claim 1, wherein the first output signal isa signal of which a voltage periodically varies with a rotation of themotor, and the second output signal is a signal of which a voltage isfixed.
 3. The motor drive control device according to claim 1, whereinthe external output terminal is connected to an output terminal of thefirst drive circuit, and the first output signal is a signal output fromthe output terminal of the first drive circuit.
 4. The motor drivecontrol device according to claim 1, wherein the signal output circuitoutputs an output signal indicating that any one of the first systemcoil and the second system coil is in the open state, when any of thefirst voltage and the second voltage is equal to or more than apredetermined value.
 5. A motor drive control device driving a motorhaving a first system coil and a second system coil, the motor drivecontrol device comprising: a first drive circuit controllingenergization of the first system coil; a second drive circuitcontrolling energization of the second system coil; and a signal outputcircuit detecting a first voltage that is a voltage at a middle point ofthe first system coil and a second voltage that is a voltage at a middlepoint of the second system coil, and outputting an output signalconcerning whether or not any one of the first system coil and thesecond system coil is in an open state, based on a detection result ofthe first voltage and a detection result of the second voltage, whereinthe signal output circuit includes a comparison unit comparing the firstvoltage with a reference voltage and comparing the second voltage withthe reference voltage, and a switching circuit outputting a switchingsignal, based on a comparison result of the comparison unit, and outputsthe output signal in accordance with the switching signal.
 6. The motordrive control device according to claim 5, wherein the signal outputcircuit further includes an output signal holding circuit holding thecomparison result of the comparison unit for a predetermined timeperiod.